Conventional spun yarns are normally made by ring spinning or open-end spinning. While such methods produce good quality yarn, there are certain restrictions and complications associated therewith. For instance open-end spinning systems have rather restrictive limitations as to staple length, rotor speeds, twist directions, wrapper fibers, fibers per cross-sectional area, and fiber bending modulus, stiffness, and other properties. According to the present invention, an apparatus and method are provided which seek to eliminate a number of the restrictions associated with open-end spinning, and in general to provide for the production of spun yarn in a simple, uncomplicated manner. The yarns produced according to the present invention have somewhat different appearance and construction characteristics than conventional spun yarns, but definitely have a spun appearance.
The basic apparatus according to the present invention comprises a hollow shaft with at least a portion of the entire circumference thereof being perforated, and mounted for rotation about an axis coincident with the direction of movement of fibers being spun into yarn. The fibers are fed into a first end of the hollow shaft, and the produced yarn is withdrawn from the second end of the hollow shaft. The shaft is caused to rotate at high speed, and a vacuum is applied to the exterior of the shaft to supply an attractive force to the free ends of the fibers interior of the shaft. Both these functions are accomplished by disposing the perforated portion of the shaft in a housing, attaching a plurality of radially-extending vanes to the perforated portion of the shaft, connecting one portion of the housing interior to a vacuum source, and connecting an opposite portion of the housing interior to a source of ambient air (or other gas). The vacuum sucks ambient air through the housing interior, the air acting upon the vanes to effect high speed rotation of the shaft, and at the same time the vacuum acts upon the interior of the shaft, imparting rotation to fibers within the shaft.
The apparatus according to the invention may be fed by either free fibers, to produce an open-end type spun yarn, or may be fed by fibers in a sliver or roving fiber mass.
To produce an open-end type yarn according to the invention, a sliver or roving is passed to a combing roll assembly, and the free fibers produced--which have a staple length of about 1 inch to 6 inches--are passed to a collector roll assembly. The collector roll is grooved, and has means defining perforation in its groove. A portion of these perforations (e.g. about 3/8 of the groove circumference) are connected up to a source of vacuum, fibers being aligned therewith and passed to the first end of the rotating perforated shaft. Delivery rolls, with the nip therebetween in-line with the shaft axis, withdraw the formed yarn from the shaft second end, and the yarn is taken up on a take-up roll. The fibers when introduced into the shaft are attracted to the shaft interior and rotate with the shaft while moving linearly along the shaft axis. The shaft rotation fully controls the fibers interengagement.
Spun-type yarn produced according to the present invention may be produced from a wide variety of types of fibers, such as cotton, polyester, rayon, acrylic, wool, mohair, etc., the spinning process not being as dependent upon bending modulus or stiffness of the composite fibers as is conventional open-end spinning. According to the invention, open-end type spun yarn can be formed with fewer fibers per cross-sectional area, and the yarn will have real twist, either "Z" or "S" direction twist. Restrictions on the end use of open-end type spun yarn according to the invention would not be comparable to conventional open-end spun yarns, but rather would be more comparable to conventional ring spun yarns.
According to another aspect of the invention, yarn produced from sliver or rovings that are fed to the vacuum spinning apparatus according to the present invention has unusual characteristics compared to conventional ring-spun yarn. The sliver or roving is fed to a draft system, wherein approximately 40-60% of the fibers within the sliver or roving mass are nipped so that these fibers are held tight. The remaining 60-40% of the fibers have loose ends, and of this group approximately 10-15% are loose on the surface of the fiber mass. When the fiber mass is fed into the rotating perforated tube, free ends of the fibers are attracted to the tube surface and rotate with the tube, being held substantially linearly stationary while the fiber mass is linearly moving along the axis of rotation of the tube. With rotation of the perforated shaft at least about 18 revolutions per inch of sheath fibers drawn through the shaft (e.g. 18-30 revolutions per inch), the free fiber ends are wrapped around the fiber mass and hold it tightly.
The end yarn produced according to the immediately-above described method has some fibers wrapped around the fiber mass in a linear direction, while others show a reverse fold wrap, and have a unique construction and appearance.
It is the primary object of the present invention to provide for the simple, effective production of spun yarn. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.